Foot valve



March 10, 1942. A BOYNTON 2,275,417

FOOT VALVE Filed Nov. 28, 1938 2 Sheets-Sheet l ALEXANDER BOYN TON,

"g: 2. ATTORNEYS.

A. BOYNTON FOOT VALVE March 10, 1942.

2' Sheets-Sheet 2 Filed Nov. 28, 1938 Fl'g 10 Fig. 8.

ATTORNEYS.

Patented Mar. 10, 1942 UNITED STAT h FOOT VALVE Alexander Boyntcn, San- Antonio, Terr.

' Application November 28, 1938; SerialNo. 242,175

13 Claims. ((31. 103-234) My invention relates to a method and means oilifting liquids fromwells by'utilizing th force of gaseouspressure fiuid confined in the annular space-between the wellcasingandthe eduction tube to aerate the liquid in the. eduction, tube if the liquid level is comparativelyhigh and, thereafter, when the, liquid level has been lowered, to expelthe same in slugs by successively. and automatically admitting slugsiof well liquid of predetermined vweightinto the eduction tube, and

then admitting gaseous ,pressure fluid under each slug to expel it from the. well by the force of expanding the gas.

One of the objects is=to overcome the usual highstartin-g or kickoff pressureslotherwise rea quired to initiate flow, to-cheapen the operation, and to increase the production by employing air or gasat low pressuresto expel} the wellliquid by sluggingafter theaccumulatedjheadlhas been discharged. h

A further object is to maintain a relatively low gas-oil ratio by expelling slugs with a minimum of aeration. v 1 n I A still further object is to-provid means to maintain the highest possible bottomhole pressures consistent with the desired amount of liquid production in. combination-with thelowest gas-oil ratio obtainable, it being possible to adjust the air or gas pressure atavalue -that will cause the production toexactlyequal a predetermined amount irrespective. of whether the well. is flowed with its own or input gas. The construction, installed upon of an eduction tube .within a well the lower end casing closed around the-tubeproximate the ground surface,

employs two valves, onewithin the other; The inner valveseats upon the'outer valve, theouter valvehaving'impaired clearance within'a tubular member and a seat upon another tubular memher above it. A latch is employed to. holduthe inner valve yieldably: seatedagainst a predetermined force. 1 A 1 A weight is'employed to hold the movableassembly of valves andrlatch in the-lower position with the inn-er valve seated until apredetermined'pressure fluid force raises the movable assembly of valves, weight, and latch, and seats the outervalva'afterwhich the inner valve isunseated by the force ofwell' liquid and pressure fluid. Back pressure oi'well liquid then unseats the outer valve; whereupon all movable parts are returned to the lower position by force of the weight member which, in landing, springs the latch. The movable assembly'is housed withupon the outer valve in a tubularwcase through whichwellliquid and pressure fluid alternately flow. M

Aerating devices may; be' spaced at intervals in theflow tubing to-unload the well down to the level where this invention will function as a slugging-means; i h v The invention consists in the construction, combination, andarrang'ement {of parts hereinafter described, and claimed, and-illustrated in the accompanying:drawingsinlwhich: v I ,Fig, 1 is a.vertical sectionof.v a well equipped with this device installed within the bracketed space ,A, theinner portion of the device being shownin elevation. Y r 1 Fig. 2 is a Vertical section or thev devicelwith its working partsinthe lower position; h Fig..3.is mainly a verticalsection ofthedevice withits workingparts in the upper position, the lower end thereofibeing shown in elevation. Fig. 4 is aho'rizontal'section on the line Fig.2.

Fig. 5 is a horizontal section on the line-5+5, Fig..2..,..,

Fig..6 is. a horizontal section on the line 6-5,

Fig.7 isahorizontal section on the line 1-1, Fig.2. i I

1 Fig, 8 is avertical section of'a part of the devic'eon, the line .8 -..8.,,F g. r

Fig. 9 isla horizontalsection on th line 9-9, Fig. 2.

Fig. 10 is a vertical sectionv or the device shown'inFigiii. v Fig. 11, is a horizental section on the line ll -'ll,'Fig.2'.. a

Fig. 1:2'is a, vertical section of a portion of a modified form of the invr'entiorn l Fig.fl3 is a horizontal'sectionon the line 13-!3,

igL I The same characters refer, tothe same parts throughoutthe several views.

The flowtubing connection 9, upper housing nipple IB', valve seat member] I', lower housing nipple I2, and anchor. joint connection 13 form the outer shellwithin which the landing-weight 28 normally lands its legs 28a uponthe upper end ofconnection 13. The upper endoi landing weight 28. is threadedly connected to latch housing nipple I9. This nipple is in turn threadedly engaged at itsupper end to lower extension Ila ofgvalv'e and valve seat member I! having lateral openings llb, valve seat I10, and chamber Md. The engagement between members I! and I9 is secured by lock ringvl 8..

Within valve and valve seat member thelower end of f1, valv member I6 has a close working fit. Vertical passage I601, within tubular section I'Sa, communicates with lateral openings I61) and IE0, the upper portion of member I6 being enlarged to form a valve which normally engages a valve seat IIc. Nipple I5, which may contain lead or other substance I511 to give it correct weight to cause the desired difference between the Weight of the slug and the value of the pressure fluid, is threadedly connected to valve member I6 and to up-. per weight member I4 which has a four way finned extension I 4a having an easily movable fit within the central opening through connection 9.

The lower end of valve member I6 has threaded engagement with latch shaft 20, the upper portion of which has a close working fit through a central opening within extension I'Ia. The central enlarged portion of shaft has a free sliding clearance within the central opening through ball roof 23; and the'lower end has a close sliding fit in the central vertical passage 280 in the upper end of member 28. Upon the threaded portion of shaft 20, ball floor 26 is engaged and secured by lock nut 21. Spacer pipe '22, the upper end of which has a free sliding fit within the centralopening inthreaded extension IIa, is threadedly joined to the cupped upper end of ball roof 23. Latch spring 2| has clearance over nipple 22 and free clearance between it and the wall of nipple I9. This spring, installed somewhat compressed, is held in a fixed position at its upper end by the lower end of extension I'Ia. The lower end of this spring rests upon the upper end of ball roof 23.

The expansive force of compressed spring 2| impinges latch balls between the oppositely inclined adjacent surfaces of ball roof and floor urging the balls outward against latch sleeve 24, which may be pressed into nipple I9 and landed upon a shoulder I 9a as shown. The opening through sleeve 24 is of such diameter as will force the latch balls inwardly, somewhat less than one half the diameter of the balls from their extreme outer position at either end of the latch travel. The longitudinal peripheral slots 24a serve to allow free movement of the lubricant within the latch chamber in order to prevent partial impingement upon thelubricant in the downward stroke of the movable parts within thelatch.

The position of the latch balls can be adjusted vertically by screwing the ball floor 26 upward or downward on shaft 20, and the vertical travel of the latch may be regulated by slightly lengthening or shortening spacer nipple 22 which, at the upper end of its travel, lands upon the member I1. The length of nipple 22, in addition to governing the latch travel, also stops valve member I6 in proper position to allow fluid to pass through it without abrading. valve seat Ilc, as appears in Fig. 3. In latching the balls roll part way over the ends of sleeve 24 as is apparent, the balls being held from escaping outwardly by the peripheral cupped portion of the roof and floor, as appears, provision being also made for some clearance between the balls and shaft 20 at the extreme inward position of the balls as they pass through sleeve 24. The latch chamber within nipple I9 should be filled with a lubricant, the escape of which is prevented by the close fit of shaft 20 within the bore at either end.

Manifestly, the latching force is governed by the compression energy of spring 2I, and by the extent of the outward travel of the latch balls over the curved ends of sleeve 24.

It can be observed that the lower end of shaft 20, movable within the bore 280, serves to maintain the displacement of this shaft within the latch chamber at a constant value; that is, when the shaft moves upward, the lower end of the shaft is entering the chamber as the upper end is leaving, and vice versa. Therefore, the latch chamber within nipple I9 does not breathe during the movements of the latch.

Manifestly, to accomplish this constant dis-' placement, both ends of the shaft must be of the same diameter as shown.

The mechanism above described is installed within the bracketed space A, Fig. 1, by threadedly joining flow tubing connection 9 to the lower end of the flow tubing. Perforated anchor support 2b, closed by cap 20, may extend to the bottom of the well B and support the flow tubmg.

Pressure fluid to operate the device is confined in the annular space Ia between the flow tubing 2 and well casing I. This fluid may be gas originating within the well or may be supplied from an external source through nipple 8. The necessary seal between the flow tubing 2 and well casing I, proximate ground surface G, is accomplished in Fig. 1 by casing head base 3, cap 4, plate 5, seal ring 6, weld 5a, and bull plug I, as is old and obvious.

One or more aerating devices 2a, such as is described in either of my following patents: 1,470,053, 1,517,611, 1,686,262, 1,712,418, 1,747,- 570, 1,747,571, 1,747,572, 1,749,124, 1,767,201, 1,767,202, 1,768,109, 1,768,110, 1,770,023, 1,772,036, 1,773,942, 1,773,943, 1,779,726, 1,779,727, 1,784,720, 1,793,671, or 1,952,581 may be placed in the flow tubing at intervals of approximately to 500 feet, depending upon the well condition and value of the pressure fluid used in flowing the well. The use of such aerating devices reduces the initial pressure required to unload the well down to proximate the level of the device disclosed in this application.

The operation of this invention, after the accumulated head of well liquid has been discharged from the well above transverse passages 281) by the combined action of the aerating devices 2a and this invention will now be briefly described. It is assumed that air or gas of suflicient volume and pressure to flow the well is confined in the annular space Ia between the well casing and flow tubing. The movable assembly is at rest in the lower position shown in Fig. 2.

Air or gas in the annular space between well casing and flow tubing follows the previously expelled well liquid into the flow tubing. The velocity of the air or gas entering the flow tubing via perforations l2a, I2b, and through the central opening in connection I3 passing into the eduction tube by flowing around member I'I, through the annular space exterior of nipple I5 and weight member I4, and between fins I4a. increases rapidly as the last of the accumulated well liquid is expelled from the flow tubing. The lifting force of this pressure fluid, accompanied by a certain amount of well liquid in spray form, quickly lifts the movable assembly because of the resistance oifered to the pressure fluid and liquid spray in passing through the restricted annular clearance between valve I1 and nipple I2, some additional lifting resistance being also developed in the less restricted annular space around members 14', l5, l9, and 28. Valve surface He seats upon its seat Ha, thus stopping, for the time being, further escape of pressure fluid and well liquid through the flow tubing. The movable assembly is now in theposition shown in Fig. 3, except thatvalve IE- is still seated in the position shown in Fig. 2. Well liquid now comes into the well'from-the producing formation through perforations P; Pressure fluid, at the same time, is entering and building up' pressure within the annular space la,- the operation of'the device being identical whether the wellproduces enough gas to flow it or whether pressure fluid is partially or entirely supplied from an external source through nipple 8. 1

When the pressure of the well liquid entering through openings I'lb, under inner valve member i6, plus the air or gas pressurein the annular space la builds up to a predetermined value. the latch will be sprung and valve I6, nipple l5, and weight member M will be quickly raised to the position shown in Fig. 3.

Part of the pressure that held valve "seated in its upper position, shown in Fig. 3, is now exerted above this valve due to the flow of well liquid through chamber lld, lower lateral openings I60, vertical passage Hid, and upper lateral openings Nib into the flow tubing above.- The pressure thus exerted above seated valve memher I! partially neutralizes the force that there'- tof ore held this valve seated. The entire movable assembly, therefore, falls. In falling valve l6 remainsopen as shown in Fig. 3, until weight 28 lands upon connection l3. The impact of this fall springs the latch-,irom' its upper'to its lower position, completing the operating cycle and returning all movable parts to the position shown in Fig. 2.

Briefly summarized, valve I1 is seated by air or gas pressure and is unseated by fluid back pressura Valve I 6 is unseated by'liquid pressure plus air or gas pressure, and is seated and latched by impact of the falling weight.

- The falling'movement of the movable assembly 1 is made more forceful by passages 12b, proximately below valve seat I la, due to the fact that the restricted clearance around valveseat member H (.010" to .025 being workable) makes openings |2b the path of least resistance from the annular space Ia into the flow tubing. As soon as the falling movement begins, the increased pressure above member I I, due'to the inrush of well liquid through openings I21); causes the movable assembly: to fall with. increased Perforations [2b should be large enough to admit the well liquid fast enough to allow the desired rate of production, but these holes must not be so large as will cause the back pressure of gas escaping through the flow tubing. following the slug to prevent valve H from seating.

M holes", each /g" to diameter; .will be; found approximately' correct for 2! flow tubing. l 'It' will be observed thattheigreate'r the weight valueofi. weight. member l4 and nipple l5, and the :greater distance thev movable assembly falls whenf valve IJ' unseats, the greater will be the force of the impact when. the landing weight strikesiconnection l3; I

.-'It 'will also be observedthat. the latch can be made to hold with different forces. in the upper and lower positions,:by. allowingthe latch balls to roll farther outward for more latching force, and. vice versa,.as beforestate'd. Thus. anyndesired value of fluid force: canbe. caused. to. open valve "hand a much lesser force can be made to=closeit by the landing impact.

Obviously, the-force with which. the latch holds, when the balls are engaged upon the. up-- per curved surface of sleeve 24, must-be such that thelandingimpact will spring the latch when the movable assembly falls. will oftenfunction better withthe latch entirely unengaged atf the-top. It isalso apparent that the greater: theforce with whichthe latch holds when. the balls are engaged. upon the lower curvedsurface of'sleeve 24, the greater must be the sum of the liquid and pressure fluid force required to spring the latch in order to open valve .16... thereby admitting the slug v into the flowtubing =-The latch. must be adjusted to. hold valve l6 seated with such force that the combined prese sure. of. theslug (still in the-annular: space la) andithe pressure fluid will be required to spring the latch, unseating'valve l-B. Reducing the; air or gaspressure: in the annular. space l'aqwill, therefore, increase the: weight. of. liquid required to open the valve I6, and consequently increase theweightiof theslugto be expelled. Corollarily,

increasing. the-airor gas pressure will lighten the slug; I

It: should be. furtherobservedthat the air or gaspressure per square inchwithin the annular space Id should be: somewhat greater than the pressure per square inch at the base ofthe'slug when it has. entered the flow tubing; If the slug pressure: at its base should be greater than the force of. the pressure fluid, the aerating devices 2a will have. to flow out of the upper portion of the slug before the remaining portion will lee-ex-v pelled... Such a flowing condition indicates that the air or gas pressure should be increased until the slugs occur at regular intervals, and are expelledjwithout appreciable aeration.

lithe slugs are too short to afford a. satisfactory gas-oil ratio, the air or gas pressure shouldbe reducedluntil the Weight'of the slugs is suchthat thev air' or; gas pressure will expel them: at such; intervals as'will keep the well'liquid headldown low enoughto allow thedevice to produce by slugs, unaidedby the aerating devices 2a, the latter being properly. employed only tounload' the wellafter a period of standing. If theproductionof the..well;is.so great that this result-cannot be attained with. the device as installed, the latch. should be-adjusted to hold valve The :device is operated by liquid pressure such as described in my Patent No. 1,952,581 will be found to afford a better gas-oil ratio than the difierential type of such devices. If aerating devices of the type here recommended are employed, they should be adjusted to intake air or gas into the flow tubing at a pressure within them 'of slightly greater value than the pressure used to flow the well by slugs. Such devices will not then admit air or gas from the annular space la. to enter the flow tubing as the slugs pass by them, but they will remain inoperative while the device is expelling slugs. Such employment of said aerating devices will, however, require that air or gas at a slightly higher pressure be used to unload the accumulated production than will subsequently be required to operate this slugging device.

Fig. 12 shows that a spring 29, freely movable within nipple it, may be substituted for the weight member M in Figs. 2, 3 and 8. The spring, installed under some compression, is held against flow tubing connection 9 by the finned support 35} threadedly engaged upon nipple l5. If a spring is used instead of a weight member, the free length of spring should be at least 10 times greater than the travel of the movable assembly and should be installed compressed at least 50% of its free length, in order that the expansion force of the spring will not become unduly spent before the movable assembly is returned to its lower position.

It will be understood that the foregoing drawings and specification are illustrative and not intended to limit the construction or uses of this invention which may be greatly varied within the scope and purpose thereof.

I claim:

1. A foot valve for Wells to control the periodic discharge of slugs of liquid including, an eduction pipe, a freely movable valve assembly closely fitted therein and adapted to be raised when the resistance to the flow of fluid through the pipe is sufiiciently reduced, a seat to be engaged by said assembly to close the pipe, and a valve within said assembly to thereafter open upon the accumulation of a predetermined pressure therebelow so as to release the accumulated pressure thru said assembly whereby the assembly will drop away from said seat and the rate of flow will again increase until the resistance to flow again raises the assembly.

2. A control valve for wells including, an eduction tube, a seat therein, a valve to be raised against said seat by the flow of fluid when the back pressure due to liquid in the eduction tube above said seat is decreased to a predetermined value so that the eduction tube is closed, and means operable upon the building up of a predetermined pressure below said valve to release such pressure thru the valve so that the valve will move from the seat by gravity and the increase of the back pressure in the tube due to the flow of liquid thru said means and past said valve.

3. A control valve for wells including, an eduction tube, a seat therein, a valve to be raised against said seat by the flow of fluid when the back pressure due to liquid in the eduction tube above said seat is decreased to a predetermined value so that the eduction tube is closed, and means operable upon the building up of a predetermined pressure below said valve to release such pressure thru the valve so that the valve will move from the seat by gravity and the increase of the back pressure in the tube due to the flow of liquid thru said means and past said valve, and additional means to latch said first means to open only at said predetermined pressure below said valve.

4. A control valve for wells including an eduction tube, a seat therein, a valve to be raised against said seat by the flow of fluid when the back pressure due to liquid in the eduction tube above said seat is decreased to a predetermined value so that the eduction tube is closed, and means operable upon the building up of a predetermined pressure below said valve to release such pressure thru the valve so that the valve will move from the seat by gravity and the increase of the back pressure in the tube due to the flow of liquid thru said means and past said valve, and additional means to latch said first means to open only at said predetermined pressure below said valve, said last means being adjustable to vary the rate of operation.

5. A foot valve including a valve, a second valve movable therein, and latch means to hold said second valve in either closed or open position to cut off or allow a fiow of fluid thru said first valve.

6. A foot valve including a valve, a second valve movable therein, and latch means to hold said second valve in either closed or open position to cut off or allow a flow of fluid thru said first valve, said means including a ball and sleeve latch.

7. A foot valve including a valve member, a second valve member movable therein, and latch means to hold said second valve member in either closed or open position to cut off or allow a flow of fluid thru said first valve member, and a weight member on said second valve member tending to close said second valve and open said first valve member.

8. A foot valve including a valve member, a second valve member movable therein, and latch means to hold said second valve member in either closed or open position to cut off or allow a flow of fluid thru said first valve member, and spring means on said second valve member tending to close said second valve and open said first valve member.

9. In a slugging foot valve for wells, the combination of a well casing having well liquid therein, an eduction tube extending into said liquid, sealing means between said tube and easing proximate the upper ends thereof, pressure fluid above the well liquid, means for replenishing said pressure fluid, an annular plate proximate in the lower end of said tube and transverse thereof, said plate having a central opening for the alternate admission of well liquid and pressure fluid, a valve assembly in said eduction tube, said assembly normally resting upon said plate, a, valve seat insaid eduction tube, said seat being in spaced relation to said assembly, an annular valve of said assembly engageable with said seat and hav ing an impaired clearance therearound for pressure fluid to exert liftin force thereon to raise said valve to engage said seat at a predetermined velocity of said fluid, an axial opening in said valve, said opening having pressure ports communicaitng with the exterior thereof below the impaired clearance area and an annular valve seat surrounding the upper end of said axial opening, a second valve within said last axial opening and adapted to engage the seat around said opening, said second valve being adapted to be opened by combined force of well liquid and pressure'fluid so that said liquid and fluid may flow therethrough and to be closed by impact of said assembly upon said annular plate after the force of such well liquid becomes increased to a predetermined value in the eduction tube above said valves, a weight assembly extending upward from said second valve, a shell extending downward from said first valve, a Weight upon said shell, lateral openings in said eduction tube below said seat to influence the movements of said assembly by apportioning the rate of fluid flow into said tube above and below said first valve, and lubricated latching means within said shell, said means being adapted alternately to support said second valve in closed and open positions.

10. In a slugging foot valve for wells, the combination of a well casing having well liquid therein, an eduction tube extending into said liquid, sealing means between sad tube and easing proximate the upper ends thereof, pressure fluid above the well liquid, means for replenishing said pressure fluid, an annular plate proximate the lower end of said tube and transverse thereof, said plate having a central opening for the alternate admission of well liquid and pressure fluid, a valve assembly in said eduction tube, said assembly normally resting upon said plate, a valve seat-in said eduction tube, said seat being in spaced relation to said assembly, an annular valveof said assembly engageable with said seat and having an impaired clearance therearound for pressure to exert lifting force thereon to raise said valve to engage said seat at a predetermined velocity of said fluid, an axial opening in said valve, said opening having pressure ports communicating with the exterior thereof below the impaired clearance area and an annular'valve seat surrounding the upper end of said axial opening, a second valve within said last axial opening and adapted to engage the seat around said opening, said second valve being adapted to be opened by combined force of well liquid and pressure fluid so that said liquid and pressure fluid may flow therethrough and to be closed by impact of said assembly upon said annular plate after the force of such well liquid becomes increased to a predetermined value in the eduction tube above said valves, a weight extending upward from said sec- I end valve, a shell extending downward from said first valve, lateral openings in said eduction tube below said seat to influence the movements of said assembly by apportioning the rate of fluid flow into said shell above and below said first valve, and latching means within said shell, said means being adapted alternately to support said second valve in closed and open positions.

11. In a slugging foot valve for wells, the combination of a well casing having well liquid therein, an eduction tube extending into said liquid, sealing means between said tube and casing proximate the upper ends thereof, pressure fluid above the well liquid and means, for replenishing said pressure fluid, an annular plate proximate the lower end of said tube and transverse thereof, said plate having a central opening for the alternate admission of well liquid and pressure fluid, a valve assembly in said eduction tube, said assembly normally resting upon said plate, a

valve seat in said eduction tube, said seat being in spaced relation to said assembly and having an impaired clearance assembly for pressure to exert lifting force thereon to raise said valve to engage said seat at a predetermined velocity of said fluid, an axial opening in said valve, said opening having pressure ports communicating with the exterior thereof below said impaired clearance and an annular valve seat surrounding the upper end of said axial opening, a second valve within said last axial opening and adapted to engage the seat around said opening, said second valve being adapted to be opened by combined force of well liquid and pressure fluid so that said liquid and fluid may flow therethrough and to be closed by impact of said assembly upon said annular plate after the force of such well liquid becomes ilncreased to a predetermined value in the eduction tube above said valves, a weight extending upward from said second valve, lateral openings in said eduction tube below said seat therein to influence the movements of said assembly by apportioning the rate of fluid flow into said tube above and below said first valve, and latching means within said shell, said means being adapted alternately to support said second valve in closed and open positions.

12. In a slugging foot valve for wells, the combination of a well casing having well liquid therein, an eduction tube extending into said liquid,

, sealing means between said tube and casing around the valve of said proximate the upper ends thereof, pressure fluid above the well liquid, means for replenishing said pressure fluid, an annular plate proximate the lower end of said tube and transverse thereof, said plate having a central opening for the alternate admission of well liquid and pressure fluid, a valve assembly in said eduction tube, said assembly normally resting upon said plate, a valve seat in said eduction tube, said seat being in spaced relation to said assembly, an annular valve of said assembly engageable with said seat, impaired clearance around said valve for pressure fluid to exert lifting force thereon to raise said valve to engage said seat at a predetermined velocity of said fluid, an axial opening in said valve, said opening having pressure ports communicating with the exterior thereof below said impaired clearance, an annular valve seat surrounding the upper end of said axial opening, a

second valve within said last opening and adapted to engage the seat around said opening, said second valve being adapted to be opened by combined force of well liquid and pressure fluid so that said liquid and fluid may flow therethrough and to be closed by impact of said assembly upon said annular plate after the force of such well liquid becomes increased to a predetermined value inthe eduction tube above said valves.

13. A slugging foot valve for wells comprising in combination a well casing having well liquid therein, an eduction tube in said casing to provide an annular space, said tube extending into the liquid, an annular space between said tube and casing above such liquid, pressure fluid in said space, a seat in said tube, two valves, one within the other, the first of said Valves being adapted to engage said seat, the second of said valves having a weight thereon and being adapted to seat .upon said first valve, pressure fluid being employed to seat said first valve to close the eduction tube, the well liquid co-acting with the pressure fluid being employed to unseat said second valve to open said eduction tube, means to apply the Weight of well liquid at a predetermined value to unseat said first valve, said second valve being seated by the falling impact of said valve and said weight to alternately admit slugs of well liquid and pressure fluid to said eduction tube and expel said liquid therefrom.

ALEXANDER BOYN TON 

